Jun Hyuk Kim's Blog

[TerrariaDB] Developing TerrariaDB (Day 1)

junhyuk1229 — Thu, 2 Nov 2023 18:42:54 +0900

Starting a new project to keep my coding skills and learn some basic js + front-end.

Recently I started playing a game called Terraria in steam. This game has lots and lots of items and I wanted to get a resource (Either from websites, programs or files) to help me get all the items in it. The problems is keeping a notepad of all the stored items is going to get tedious and also annoying using ctrl+f all the time. So I am trying to create a page for it.

It will of course have all the normal features of marking an item as done and searching the item. Some of the other feature I am thinking of creating is...

Mark an item as sellable (Some items are made from others so selling them might be a problem later)
Get a list of raw materials for crafting all the missing items
Get number of ingredient items needed to craft all other items that has the ingredient item as its crafting recipe
Mark some items that might be needed constantly (Ex: consumables, throwables, etc)

The above features might be secondary to what I really want but I will try to add features one by one. Currently I am creating a page using vue as the frontend and fastapi as the backend. I might upload this page to the internet, but probably not.

[Python] About round function in python

junhyuk1229 — Fri, 22 Sep 2023 13:50:12 +0900

So this happened when I tried to solve a programming problem using python's round function.

Some errors from test cases were found and I was trying to find out why those errors were happening.

round(0.5) = 0 ???
round(1.5) = 2
round(2.5) = 2 ???

The rounding that we learn usually is where the number is rounded up if the number after the decimal is 5 or larger. So why are the results above happening?

The python function round uses the 'to nearest, ties to even' as the standard to round the number hence the results being only even. The standard we are used to is the 'toward +inf' way, so how can we use the original formula without using the round function? My solution was to make a function to get the results.

def round_digit(x):
	# Get float after period
	temp_float = x - math.floor(x)

	# If float is less than 0.5
	if temp_float < 0.5:
		return math.floor(x)

	# Else
	return math.ceil(x)

[2023/08/07] Daily Review

junhyuk1229 — Mon, 7 Aug 2023 21:25:21 +0900

Started writing my papers to get a job, it is due tomorrow. I do want to finish the project while the servers are up.

Tomorrow I'll starting making the tables for the database. Some files are currently loaded by using a csv file and loading it. I don't know if this is faster. I do think that loading the csv and making adjustments using pandas is slower than making the query for MySQL.

I also need to test the new prediction method. The method might take more time than the original. We will have to test both methods in terms of time.

[SSH] Transfering files between servers

junhyuk1229 — Mon, 7 Aug 2023 21:21:03 +0900

SCP, or secure copy, is used in linux to copy files from one loaction to another securly. Using the key of the other server we can connect the two using scp and send(copy) files. A password can be used but most of the times a key file is used to determine its validity.

This file transfer was used to transfer a file crawled in a AWS EC2 server to another server.

Copy a file to another server

scp -i key_folder/key_name transfer_file_folder/transfer_file username@server_ip:destination_folder

Copy a folder to another server

scp -i key_folder/key_name -r transfer_file_folder username@server_ip:destination_folder

[Backend] CORS

junhyuk1229 — Sun, 6 Aug 2023 20:03:31 +0900

CORS or Cross-Origin Resource Sharing is an error we encountered when connecting the backend(fastapi) and the frontend(node.js). When connecting the two the following error happened

Access to fetch at 'URL_1' from origin 'URL_2' has been blocked by CORS policy

So I had to search about the CORS policy and here are the basic findings...

So what is CORS?

CORS is Cross-Origin Resource Sharing and is used to prevent other domain requests.

So if, for example, domain-a.com requests a HTTP request to domain-b.com it will be automatically blocked by CORS

CORS only allows, by default, same-origin access is allowed.

Why is CORS needed?

CORS is needed to prevent malicious or unwanted domains from accessing your domain and get important information from HTTP requests.

How to allow CORS in fastapi

CORS can be enabled using the middleware package in fastapi. The following code was used to solve my issues during the project.

from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware

# Add CORS to application / API
app = FastAPI()
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

Of course allowing all origins, methods and headers are probably not a great practice.

allow_origins: domains
allow_methods: HTTP method ('PUT', 'GET', etc.)
allow_headers: HTML headers

Probably allow_origins needs to be changed to get better security but if the project is just a test / solo projects.

Used Sites

https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS

Cross-Origin Resource Sharing (CORS) - HTTP | MDN

Cross-Origin Resource Sharing (CORS) is an HTTP-header based mechanism that allows a server to indicate any origins (domain, scheme, or port) other than its own from which a browser should permit loading resources. CORS also relies on a mechanism by which

developer.mozilla.org

https://fastapi.tiangolo.com/tutorial/cors/

CORS (Cross-Origin Resource Sharing) - FastAPI

FastAPI framework, high performance, easy to learn, fast to code, ready for production

fastapi.tiangolo.com

https://medium.com/tribalscale/stop-cursing-cors-c2cbb4997057

Stop Cursing CORS

Most people doing frontend development at some point deal with CORS issues. The problem is that most people don’t know what is happening…

medium.com

https://hackernoon.com/understanding-cors-why-its-important-and-how-it-works

Understanding CORS: Why It's Important and How it Works | HackerNoon

This article will explain what CORS is, how it works, and why it is important.

hackernoon.com

[2023/08/06] Daily Review

junhyuk1229 — Sun, 6 Aug 2023 18:55:55 +0900

Just finished my study in AI. While this is not the education that I anticipated, it was the best education for me to use other programs that I would never use.

For the final project we used AWS services(RDS and EC2) and fastapi to connect the frontend.

Just had Thursday, Friday and the weekend as a resting time after the final project. I will start reviewing, keep writing daily blogs and applying for jobs from now on. Will try to add another page if I can.

[2023/06/22] Daily Review

junhyuk1229 — Thu, 22 Jun 2023 21:09:19 +0900

TODO

Work on the project
Get data from final project

Notes from Final Project

Call limit = 256 times in 15 minutes

Number of Items = 27248 -> 26.6 Hours -> Possible

Number of Users = 361149 -> 352.6 Hours -> Nearly not possible

Number of Interactions = 42426425 -> 41432 Hours -> 1726 Days -> Impossible

Some queries can be used in the front-end side, making the service about 512 times in 15 minutes. This is probably not totally correct because all front-end will be used for the user and not for the server.

[2023/06/17] Daily Review

junhyuk1229 — Sat, 17 Jun 2023 21:34:51 +0900

TODO

Finish third Kuber lecture

Get better sleep (10 ~ 11)

Fix resume and apply for feedback

Q&A

Q: What is DNS 1.1.1.1 and why is it used?

A: The DNS server for 1.1.1.1 is owned by CloudFlare. A DNS server convers the typical string website name to a IP address to the server you are accessing. It is the fastest DNS with about 11.1ms currently in terms of speed and deletes all accessing data in 24 hours from when a request is sent.

[2023/06/15] Daily Review

junhyuk1229 — Thu, 15 Jun 2023 21:24:40 +0900

TODO

Keep doing EDA to get extra features
Finish second Kuber lecture
Fix resume from feedback
EXERCISE

[2023/06/13] Daily Review

junhyuk1229 — Tue, 13 Jun 2023 21:34:20 +0900

TODO

Add extra contents to presentation
Finish first Kuber lecture
Get better sleep (10 ~ 11)
Fix resume and apply for feedback